Regarding the original topic of the post, I found a video in which someone uses an utility to create a camera profile for Darktable from an existing picture. Maybe this could do the trick for you, creating the camera profiles for every film simulation and then use them.
Hope it helps.
That has just recently been repaired…it was broken for some time… I think after v 3.6 maybe … the fix may also have come after the release of 4.2 I will have to check but it is working now…
It has been mentioned many times here on the forum and is more recently documented quite nicely here…
Edit…
Ya just last week so it would have to be compiled and run from the master branch to work at the moment…
I am running the latest git version on Manjaro/Arch/XFCE. When I start dt-chart from the terminal and import a .pfm target file nothing is displayed … but no crash now!
Are you using the LAB color space?? I will try on my end on a Win machine
This may be my problem … I do not see a place to set LAB color space
Off the cuff its a setting in your config files… tablerc search for text allow LAB… I think its set by default to false… set to true.
Now you will have an option in your output profile to do so in LAB…that is what is needed…
I can confirm it works…
EDIT
I just used a raw NEF file as it was a nice shot. I think from the post about correctly saving a reference image…
I put pickers on the tonal patches… This is how I would open the image and how I processed it… Legacy WB and none for workflow…
Its cool or towards blue as shot…
The style against test chart data so basically color corrections does a nice job…note how it nicely results in a balance from white to black…Tone curve was neutral so it was basically all from the CLUT module
DSCF5240.RAF.xmp (12.4 KB)
When it comes to match colors from OOC jpeg i find it useful the color lookup table module.
I think i got almost a pretty good match.
so does XT-* use some kind of LUT internally?
No, it is much more complicated than a LUT, but its a black box.
i am sure it is not just LUT and curves but still it probably is quite simple computationally wise.
What makes you say that?
Because the processing power on cameras is quite limited, but i might be wrong.
Yes, but the processor is tuned for image processing, it doesn’t use the same type of processor as your computer.
It’s weird because I’ve never been a huge fan of Fuji’s colours (and I’m a long-time Fuji shooter). I’m certainly in the minority, though; some people consider them sublime (I know I’m not colour blind, so maybe I just don’t have a soul 
).
Do you mean colour rendition in general or specific film simulations? Because there’s a world of difference between all the different film simulations with regard to colour. I find Velvia too gaudy, but I love Classic Neg for it’s combination of warm and cold tones, for example.
If you mean colour rendition in general, then I would probably say you’re in the minority, yes, because colour is one of the most praised aspects of Fuji’s ecosystem. But your opinion is the only thing that’s important to you and your enjoyment of photography. What do you shoot?
The colour rendition in general.
Maybe I just can’t appreciate how good they are because I’ve never used anything different? Maybe, if someone gave me a different camera, I’d be saying “Oh my good Aunt Betty! These colours are awful! Gimme my Fuji back!”
Maybe I just can’t see it until it’s pointed out? Maybe it’s just not so important to me? (I shoot street and documentary photography). No idea. Maybe (and most likely) I’m just plain weird.
I must admit I’m not sure what people are referring to when they say the “Fuji colours”, because all raw files from every manufacturer are dull and not very colourful. So, they must be talking about the JPEGs, and then you have to talk about film simulations because every JPEG from a Fuji camera uses one. The default Provia is perhaps the truest representation of the Fuji colour look, but from my experience in Fuji communities, the favourite film sims are the ones like Classic Chrome, which give that old school cool film look.
For what it’s worth, I used to shoot Canon before getting a Fuji camera, and when I process my old Canon files, I notice a difference in the colours and how I have to decrease the red in the Canon files to get a more pleasing and accurate look. I don’t have to do this with my Fuji files. But I’m not sure that really constitutes anything valuable in terms of colour rendition 
So, you’re not weird at all!
Same here, colors from canon raw were always too red / magenta. Fuji raw seems more neutral.
But the Fuji jpeg Magic is very helpful - at least for me - if I want to create a consistent look for a bigger series of images. Something I could never recreate from raw images.
My reply is not very productive, but fuji film simulations are very complicated and I don’t think one can recreate them easily.
Have a read here to get an idea of their inner working: https://www.imaging-resource.com/news/2020/08/18/fujifilm-film-simulations-definitive-guide
I don’t think we can recreate these simulations as a simple lut table.
That said, I’m a total amateur so take this with a grain of salt! You already have several good answers here.
Since Fujifilm themselves publish film simulation LUTs for their log video files, I think it’s safe to say that they can indeed be implemented as LUTs. Also note that Capture One and Lightroom and DxO, the three biggest commercial applications in raw editing, use (what amounts to) LUTs in their software to implement Fuji Film Simulations.
And lest we forget, Fuji implemented film simulations on the original X-Pro1, a woefully underpowered camera that surely didn’t have the processing power for some elaborate physical simulation.
Their marketing department has done a amazing job at creating a mystique around these fabled Film Simulations. In reality, they are fancy names for image presets like they’re available in any other camera. (And to be frank, don’t look particularly like analog Provia or Astia much at all). Still, they provide a nice look, and are maybe more thoughtfully designed than others. I very much like them and use them every day.
But at least to the limit of my understanding, they do not contain any magic pixie dust.
